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Get. 18, 1927.

J. A. SEEDE ELECTRIC F-URNACE Filed March 23. 1925 w M %/w w rm n W e Mi m 5 fihwul m u H x W Patented Oct. 18, 1927.

earner Oma A. SEEDI E, .or scnni r nc'rany, NEW YORK, ASSIGNOR 'roGENERAL ELECTRIC. ,coMrmY, A coRPoRA rIon-or NEW YORK, j

ELECTRIC regimen. I

" lic at ionlfiled March 23F125fSerial M 7357.

My-invention relates "tdeIeecr'ie' furnaces, A 1 ereparcieu'lgrl ftoelectric are; Z'furnaces and lias' for its object the provision ocean--nace f this type inwhich tli'e are ssseparated from the charge i'n anenclosed space and-"is "adjustable'in this space obtain the desiredheating efi'ect, v

Myfirlv'eiiti'on has application in the carrying out of various heatingoperations such, for-"example", "as the production of sodium sulphide'from" nit'er cakefsodium ac1d sulhidearid saltgc'ake'; ,A "charge 'thisnature asa rapid 'corrosiveefi'ect on the'lining and also-has',a"tendencyf to vaperizeirap idly when in close proiii m'ity to'anelectricare j Incarr'ying out my invention vI-provrde an enclosed spacein which, the electric arc isfseparated from the chargefand providemeansfor adjusting the electrodes to suitably adj list. the position ofthe are with i relation 'to the'chargef. I

Far a more complete understanding of my invention reference should behadto the accompanying drawing, the single figure of which shows asectionalView of an electric furnaceembodyin g my invention. 4

' Referring to the drawing, the furnace comprises refractory crucible10, the bottom of which is inclined toward an outlet opening 11;Centrally located in the crucible 10 is a tube or cylinder .12 made ofsuitable refractory material such as carbon or graphite. The cylinder 12fits tightly on the bottom of the crucible 10 and is preferably r joinedto the bottom of the crucible by means of a suitahlecement. Thecylinder112 is provided with a cover 13 made of a-simiiar material andprovided witha central aperture Mth'rOugh which extends a carbon or agraphite electrode 15. A similar electrode 16 is inserted in a centralaperture provided in the bottom of the crucible and extendsupward inarcing relation with the upper electrode 15. The electrodes 15 and 16extend loosely"throu'gh the apertures provided for them so that they maybe adjusted freely in a've'rtical direction; V

Theupper electrode 15-is adjustedautomatically by means of suitableapparatus so as to maintain an are of a predetermined length with-thelower electrode. It is moved. by means of an electric motor 17 which isconn'ectedthrough gearing 18 with a rotatable stationary nut '19,cooperating with a screw-threaded rod 20 to which the upper electrode 15is secured. The control means for the motor 17 may be ofany suitabletype. The control means shown is ofth'e type described and claimed in myPatent No. 1,449,- 251 dated March 20, 1923, and it therefore 'will notbe described in detail in this application.

Briefly, this control means comprises two switches 21 and 22, one foreach direction of rotation, which control the connection anddisconnection of the motor to electric supply mains 23 and 24. Theswitches21 and 22 are operated by means of magnet coils 25 and 26 whichare controlled by acontact making ammeter 27. This contact-makingammeter comprises a magnet coil 28 which is connected to the secondary29 of a current transformer, the primary of which constitutes a portionof the supply conductor 30, leading from one secondary terminal of atransformer 31 to the electrode 15. The opposite secondary terminal ofthe transformer 31 is connected through a conductor 32 to the. electrode16. An adjustable resistance 33 is connected across the secondary 8Ocoil 29 to enable the setting of the magnet coil to be adjusted. Themagnet coil 28 operates a contact arm 34 between two stationary contacts35 and 36, and thereby controls the energization of coils 25 and 26through conductors 37 and 38 connecting the stationary contacts 36 and 35't0 the coils 25'and 26 respectively. The opposite terminals of thecoils are connected through aconductor 39 to the supply main 23 and thecontact arm 34 is connected through a conductor 40 to the supply main24. An auxiliary control switch 41 is connected in the conductor 38.This switch is operated by" a magnet are between the electrodes and 16becomes the arc has been adjusted to the predetermined length thereduced, energization.,.0f coil 28 allows the contact arm 34 to drop anddisengage the contact 35 whereby the switch 22 isrleased and opens thecircuitof the. vmo t or. In,asiniilar 1ianner when; the arc he'comes toolongthe magnet coil 28 ,.due

to its reduce d energizatiom, allows thefcontact varrn to re gage thestationary contact 36 whereby the motor circuit is closed in the reversedirection through the switch 2l and the motor operated to lowerthe-electrode 15 until. stopped the movement of contact arm 34 awayfrom-contact 36.

The motou-is brought to rest quickly :by dynamic braking the resistance42ribeing connected acrossthe armature of the motor by means of a switch43 when bothofthe switches v2liand 122 are in open position.

Theswitch 43 is operated by a magnet coil 43'. which is connected ;across the armature of the motor. A ,mechanicalinterlock J44 preventsclosure of-theswitch 43 when either one of .the switches 21 and 22 areclosed. The field winding 17 of the 'll'lQtOl 17 is constant-lyenergized and iswconnected through conductors 45 and 46 to the supplymains 23 and 2-4. V

Should the electrode 15 be lowered too far for any reason, so that thereduced voltage across it becomes less than the voltage required tocause the coil 41 to maintain the switch 41 closed, the switch 41 willopen, thus opening the motor circuit and bringing the electrode torest.- The electrode will remain in this position until the arc hasreached an excessive length by the burning away of the electrodes.

The lower electrode 16 is raised and lowered by means of an electricmotor 47 which is connected through a gearing 48 to a rotatablestationary nut 49 cooperating with a screw-threaded rod 50 to which thelower electrode lb is secured. The motor 47 has its field winding 51'permanently connected to the conductors 45 and 46. Its armature may beconnected to the conductors 45 and 4(S by means of a suitable manuallyoperated switch 52 whereby the motor maybe started and stopped andoperated in "either direction of rotation.

It will be observed that the cylinder 12 with its cover 13 forms anenclosed space for the are between the electrodes. The charge to beheated is placed in the crucible around the cylinder 12 and the top 13.In the production of sodium sulphide, for example, the crucible may befilled around the sides of the cylinder 12 with a suitable refractorymaterial 53, such as charcoal. The niter cake, sodium acid sulphide andsalt c'al e,'as' indicated by reference numeral 54, is filledinthe'c-rueible on top of the' charcoal around the top-13 which, asshown, is provided with a cone-shaped upper surface.

"The heat from the are is conducted through. .the walls oithe cylinder12 and top 13, and

fuses thecliarg'e 54ivhich mixes and trickles down through the charcoal53, the reaction proceeding as the molten product proceeds through thecharcoal, it finally draining off through the outlet 11.,

Itwill boobservedthat the molten charge .ipasses first through a '{z'oneof gradually increasing temperature at the upper part of the cylinder 12unti l the maiimumtemperature is reached at the. point nearest the arc.The charge then'passes downward through a zone of, duallydecreasingtemperature .to the bottom of the crucible.- By mean'sfof the manuallyoperated-switch 52 the lower electrode may. be adjusted as. desired.andlthe position of the are thereby adjusted so as to bring the p ointct maii mum temperature to the position giving the most efficientoperation. When 'the, lower electrode is either raisedcr lowe'i'ed itwill be observed. that the .-upper electrode will be automaticallyraised or lowered a corresponding --amou nt since its automaticadjusting apparatus'will maintain a predetermined length of are.

TVhile I have described my invention as embodied in concrete form and asoperating in a specific manner in accordance with the provisions of thepatent statutes, it should he understood that I do not limit myinvention thereto, since various modifications thereof will suggestthemselves to those skilled in the art without departing from the spiritof my invention, the scope of which is set forth in the annexed claims.

IVhat I claim as new and desire to secure by Letters Patent of theUnited States, is:

1. An electric furnace comprising a chamber for the charge. refractorywalls forming an enclosed space in said chamber surrounded by thecharge, and a pair of electrodes extending into said enclosed space inarcing relation, said electrodes being adjustable to vary the positionof the are.

2. Jill electric furnace comprising a chamber for a charge, movableelectrodes cooperating to form an arc, refractory walls enclosing saidare through which heat is conducted to the charge, automatic means forfeeding one of said electrodes to maintain a predetermined arc, andmanually controlled .mcans for moving the other electrode to adjust theposition of the are with relation to the charge.

3. An electric furnace comprising a refractory chamber for the chargerefractory walls forming a central, enclosed space in said chambersurrounded by the charge, upper and loWer electrodes extending intomined arc, and manually controlled means for moving said lower electrodeto adjust the position of the arc in said enclosed space. In Witnesswhereof, I have hereunto set my hand this 21 day of March, 1925.

JOHN A. SEEDE.

